1. Field of the Invention
This present invention relates to a device for closing an opening of a tank or a tubular conduit and including a plate for closing the opening and movable substantially perpendicular to a plane of the opening toward the opening to be pressed against a wall in which the opening is formed, and away from the opening, the closing plate being also displaceable, in its position in which it is spaced from the opening, substantially parallel to the plane of the opening, and a piston-cylinder unit for displacing the closing plate parallel to the plane of the opening and having a housing with a cylinder bore and at least one piston displaceable in the bore relative to the housing.
2. Description of the Prior Art
Closing devices of the above-described type are well known. As a rule, they are called slide devices. The operation of such a device involves several different movements. The slide plates is moved essentially parallel to its plane to bring it into its open or closing position. In its open position, the closing plate is located sidewise with respect to the opening which it closes. In its closed position, the closing plate covers the opening. In order to sealingly close the opening, the closing plate is pressed against the sealing edge of the opening. The above-described closing devices are disclosed in U.S. Pat. Nos. 4,470,576; 3,368,792; 4,560,141; and German patent documents Nos. 3,209,217; 3,643,069; 2,528,043; 3,224,387; and 2,551,429. A common feature of conventional devices consists in that they all require expensive mechanical elements to move the plate from its closing position into its sealing position.
Accordingly, an object of the present invention is to provide a closing device of the above-described type actuation of which is substantially simplified in comparison with conventional devices.